Radio direction finder



1935- L. L. KAESS 2,023,891

' RADIO DIRECTION FINDER Filed March 10, 1931 1 2 Sheets-Sheet 1 LOUIS L. KAEss INVENTOR BYMIKK ATTORNEYS Patented Dec. 10, 1935 PATENT OFFICE RADIO DIRECTION FINDER Louis L. Kaess, Jamaica, N. Y.

Application March 10, 1931, Serial No. 521,564

4 Claims.

My invention relates to radio direction finders, and more particularly to direction finders suitable for crafts, as ships, airplanes, etc.

One object of my invention is to provide a di- 5 rection finder which is rugged and simple in construction, and easy to operate.

Another object of my invention is to provide a direction finder which is suitable to be used on a traveling craft and is adapted to receive signals from any type of transmitting station.

A further object of my invention is to provide a direction finder with which bearings can be obtained without the aid of the compass of the craft.

A further object of my invention is to provide means to indicate, for any angular direction, the extent of local electromagnetic influences on the craft, as caused by the iron masses of the craft and other local influences.

A further object of my invention is to provide means for the automatic correction of the errors caused by such local influences.

A further object of my invention is to make observations possible regardless of the direction of the craft or its relative position to the transmitting station from which the signals are received.

A further object of my invention is to obtain direct readings on the device with respect to either of the fore and aft center line of the craft, or the magnetic North Pole or the geographic North Pole.

Further objects will appear as the specification progresses.

In the accompanying drawings, which form part of this specification, Figure 1 is a front elevation of a radio direction finder embodying my invention.

Fig. 2 is a vertical section of the direction finder of Fig. 1, taken along lines 2-2 of Fig. 1.

Fig. 3 is a perspective view of the direction finder, also showing the loop antenna.

Referring to the drawings, the apparatus emor be connected with a rotatable antenna A (see Fig. 3). The antenna is preferably a loopantenna, or a combination of loop antennae of suitable design adapted to receive radio signals bodies a hollow rod or shaft ll, adapted to carry which are then transmitted to a suitable receiv- July 2, 1929, Patent No. 1,898,488, issued February 21, 1933.

The general operation of direction finders, as is well known, consists in picking up a signal of a transmitting station and rotating the antenna 5 until either a maximum or a minimum signal strength is indicated. The minimum signal corresponds with a position of the antenna in which its plane is perpendicular to the direction of the transmitting station, and the maximum signal 10 corresponds with a position of the antenna in which the plane of the antenna falls in the direction of the transmitting station.

A cylindrical casting 2 is open at the bottom, and provided with a central substantially cylinl5 drical portion 3 extending from the top of the casing bothupwardly and downwardly and constituting a bearing for thehollow shaft H, the shaft H being provided with a ring. I2, which loosely rests on top of the cylinder 3, thereby sup- 2O porting the shaft ll and permitting its rotation relative to the casing 2.

On its upper portion the cylinder 3 is provided with a peripheral recess 3 to receive a sleeve I fixedly secured to the cylinder 3. The 25 sleeve I is connected by means of a flange 6, or other suitable means, to a fixed portion of the craft; for instance, to the roof of a boats cabin, from which the casing 2 isthus supported.

A circular plate 4 is rotatably inserted at the 30 bottom of the casing 2, being preferably provided with a circular recessed shoulder 5 which extends into the casing. Clearance is provided, but the parts are so proportioned as practically to prevent dust or dirt from entering the casing. 35

A hand wheel I0 is disposed beneath the plate 4, being provided with a hub ll! having a cylindrical aperture I I to receive the end of the shaft l I, whereby the hub I0 is fixedly secured to the shaft. The plate 4 is secured to the wheel Ill 40 and the shaft II by the following means:

Projecting into the lower end of the tubular shaft H is a bolt 42, threaded on its upper end,

and provided with a winged nut 44. The wings of the nut project through corresponding 45 holes 34 of the shaft, and overlie a washer 45 surrounding the shaft on the upper surface of the plate 4. Attached to the lower end of the bolt 42 is a handle 43 which projectswith'a por- The tion of reduced diameter into the rod ll. upper face of the hub H3 contacts with a central embossing 4' of the plate 4;

The means just described provide for the en- Y gagement or disengagement of the wheel Illand plated in the following way With the handle 43 in the position shown in Fig. 2, the wheel I presses against the plate 4 and engages the latter by friction. If the handle 43 is turned in one direction-in the drawings shown counter-clockwise-the bolt 42 will partly unscrew from the nut 44, and release the pressure exerted by wing nut 45 and washer 45' on plate 4. The latter is now free for manual rotation and can be brought into any angular position relative to the wheel It and thus relative to the antenna secured thereto.

A disc I3 is fixedly mounted on the antenna shaft II by means of a hub I3 and a fastening screw I4. The disc I3 has suitably mounted, at its periphery, a cylindrical card I5, having a sinuous upper edge constituting a cam I6.

The cam I6 and the means co-operating therewith, hereafter to be explained, are provided to take care of electromagnetic influences present on the craft, which cause the direction indicated by the position of the antenna to deviate from the correct direction of a transmitting station, the direction of which is to be determined. Such influences are mainly due to iron masses onthe craft. The angular deviations between the true direction of the transmitter and the apparent direction indicated by the position of the antenna, can be determined for the craft once for all by taking observations from a transmitter of known direction and turning the ship around a complete circle, thus determining for every angular position of the antenna the deviation between the true and apparent direction.

These deviations, according to my invention, are plotted on the card I5, whereby the length of the graph corresponds to the circumference of the disc I3 and the ordinates which represent the angular deviationswhich may be clockwise or counter-clockwise, and are correspondingly plotted' above or belowa selected zero line I 6'--in a scale of proper relation to the parts with which the graph is to co-operate. Theresultant curve is of a sinuous character and when the card I5 is cut out along this curve and secured to the graph-holder I3 in the form of a cylinder, its upper edge constitutes the cam l6 for a roller 2| riding on same. a

-It should be well understood that the graph I5 is so aflixed to the graph-holder I3 that for any selected angular position of the antenna, the roller 2| rides on that portion of the cam the height of which corresponds to the deviation caused by the local influences for the selected angular position of the antenna.

In caseI use minimum signal strength observations for direction finding, which I prefer to employ, the zero line I6 is so selected that its height corresponds with the correctionrequired when the antenna plane is perpendicular to the fore and after center line of the craft. In Figs. 1 and 2, such aposition of the antenna is shown. .A narrow vertical slot 60 is provided on the casing 2,- while the graph I 5 is provided with an index 6 I whereby the index 6i opposes the aperture 60 .whenthe roller 2! comesto ride on that portion of the cam. I6 which corresponds to the fore and aft. line of the'craft.

The roller ZI, which rides on cam I6, is loosely mounted on a pin 2t of a lever I]. The lever I1 is fulcrumed by means of a two-arm yoke I'I near the lower. end of thecylindrical portion 3 of casing 2.by means of pins I8 and nuts I9.

To the outer end of the pin 2! is secured a cord 25, which passes around two pulleys 26 and 21 mounted .on the inner wall of the casing 2, the cord being attached, with its other end, to an car 28 projecting from an upper corner of a plate 28. The plate 28 is provided, on its upper and lower edges, with inward projecting roller 29-29 riding on the upper and lower edges of a rail 30 located behind the plate 28 and afiixed to the inner wall of the casing 2. The plate 28, as will 5 be hereafter explained, is adapted to be shifted along the rail 39. On the other upper corner the plate 28 is provided with an ear 29', to which is attached one end of a cord passing around a pulley 36 mounted on the inner wall of the m casing 2, and thence around a drum 31 which is mounted on the inner 'wall of the casing 2, and has within it a convolute spring 38.

The plate 28 is provided, on its front side, with a downward extending pointer 39, which co-op- )5 erates with a cylindrical scale 40 carried by the ring plate 4, and calibrated in degrees.

Opposite the plate 28 a window 4| is provided in the wall of the casing 2, which permits a portion of the scale 49 to be observed by the opera- 2Q tor. Below'the center of window M the casing carries an index mark 53 indicating the plumb line of the craft'or any fixed direction relative thereto.

As the antenna is rotated the pointer 39 moves along scale II! relative to index 50, and for any given position of the antenna will be shifted relative to the index 56 by an amount which corre sponds in degrees ofthe scale 46 with the deviation caused by the local influences for this posi- 30 tion of the antenna.

With the antenna assuming a position perpendicular to the fore and after center line (for observation of minimum signal strength), as shown in Fig. 1, the roller 2I engages a point of the cam 35 16 which falls on the zero line I6 of the graph.

The index 6| appears, through window 60, and in this position the pointer 39 points to the plumb line index 50. If the antenna is rotated into a position for which the local influences 40 cause a counterclockwise deviation from the true direction, the cam I 6 will engage the roller 2| with a correspondingly higher portion. The roller 2!, being lifted, exerts. a pullon the cord 25, and causes the latter to move the plate28 and the pointer 29 towards the right (thus countar-clockwise) relative to index 50, by an amount. which expressed in degrees of'the scale 40, is equal to the angular deviation caused in the counterclockwise direction by the local influences. On the other'han'dgif the antenna is moved into a position for which the local influences cause a clockwise deviation from the true direction, a cam portion which falls below the zero line I 6' engages the roller 2I, and the plate 28, under the action of the spring 38, is moved by the cord 35 towards theleft, thereby moving the pointer .to the left (or clockwise) relative to index 50, by an amount, which expressed in degrees of the scale it, is equal to the clockwise deviation 69 caused-by the local influences. 7

If a bearing is to be takenwith respect to the bow of tlieflcraftthat is, with respect to the fore and after'center line, the'procedure is the l w J The antenna is brought into its zero position, which incase the bearings are taken by. determining the minimum signal strength corresponds I to the position in which the plane of the antenna is perpendicular to the fore and aft center 70 line of the craft. For this end the antenna is rotated, by means of. the wheel! until the index SI of the correction, graph I5 appears through window 60.

The plate 4 is then unlocked from antenna wheel I!) by unscrewing the knob 43 and the plate 4 rotated until the zero of its scale 40 comes in juxta-position with the index 50. The plate 4 is then again locked to the wheel III by means of the knob 43 and the plate rotated with the antenna by means of wheel I!) until minimum signal strength is observed. In this position, the pointer 39 will indicate on scale Ml the correct angle which the direction of the transmitting station encloses with the fore and aft center line of the craft.

It should be noted that the corrections for the deviations caused by local influences are made automatically, due to the shifting of the pointer 39 in regard to the index 50.

In case the bearing is taken in respect to the magnetic North Pole, instead of the fore and aft center line of the craft, the procedure is the following:

The antenna is again brought in its zero position, as previously described. The plate 4 is unlocked from the wheel If! and the antenna. A reading is taken on the magnetic compass of the craft, determining the angle which the fore and aft center line of the craft encloses with the direction of the magnetic North Pole and the plate t is rotated. until its scale 40 opposes the index 50 to give a corresponding reading. Plate 4 and wheel iii are now locked and the antenna rotated together with the plate 4 until minimum signal strength is observed. The reading indicated by the pointer 39 on scale in gives the bearing in respect to the magnetic North Pole.

In case the bearing is to be taken in respect to the geographical North Pole, the antenna is again brought in its zero position as above described, and after unlocking the plate 4 from the wheel ill, the plate 4 is rotated until its scale ii] opposes the index 50 with a reading corresponding to the reading on the magnetic compass plus or minus the known compass correction. The plate 4 is now locked to wheel I!) and thus to the antenna, with which it is rotated until minimum signal strength is obtained. The pointer 39 will now indicate on scale 40 the bearing as taken in respect to the geographical North Pole.

From the above, it will be apparent that the local influences of the craft are automatically eliminated for any angular position of the antenna and irrespective whether the observations are made in regard to the fore and aft center line of the craft or the magnetic North Pole or the geographical North Pole or any other fixed direction.

It should also be noted that bearings can be taken without the aid of the compass of the craft and, therefore, the readings so obtained are independent of the known or unknown errors of the compass. Therefore, my direction finder can be used for the correction of the errors of the compass.

While I have illustrated my invention in a specific application and described a specific construction thereof, I do not wish to be limited to such application and construction, but desire the appended claims to be construed as broad and permissible in view of the prior art.

What I now claim and desire to secure by Letters Patent is: l

said shaft whereby said is made with respect to a different direction than 1. In combination with a directional antenna on a craft subject to quadrantal errors, a shaft rotatable with said'antenna; a scale; a pointer providing a normal position of reference for said scale, said scale being rotatable with said shaft; 5 said scale being adjusted to indicate substantially the angular position of said shaft with reference to the keel line of the craft; quadrantal error correcting means controlled by said shaft as it rotates to move said pointer variable distances from said normal point of reference to new points of reference in accordance with predetermined corrections for different angular positions of said shaft; and means for adjusting said scale with respect to said shaft whereby said scale reference reading is made with respect to the magnetic compass.

2. In combination with a. directional antenna on a craft subject to quadrantal errors, a shaft rotatable with said antenna, a scale rotatable with said shaft, said scale being adjusted to indicate substantially the angular position of said shaft with reference to the keel line of the craft;

a pointer providing a normal position of refer ence for said scale; quadrantal error correcting means controlled by said shaft as it rotates to move said pointer variable distances from said normal point of reference to new points of reference in accordance with predetermined corrections for different angular positions of said shaft; means for rotating said scale with respect to said shaft whereby said scale reference reading is made with respect to the magnetic compass; and a second indicator controlled by said shaft for indicating a predetermined angular position of said loop with respect to the keel line of said craft.

3. Indicating apparatus comprising a rotatable shaft, a pointer, a scale, said pointer having a normal position of reference with respect to said scale, said scale being rotatable with said shaft past said pointer to indicate the true angular position of said shaft when said pointer is in its normalposition, a quadrantal error correcting member rotatable with said shaft for displacing said pointer angularly from said normal position in an amount to compensate for the quadrantal error at all angular positions of said shaft and means for rotatingsaid scale with respect to said shaft whereby said scale indicates the bearing from true north or from the ships bow.

4. In combination with a directional antenna subject to quadrantal errors; a shaft rotatable with said antenna; a scale; a pointer providing a normal position of reference for said scale, the scale being movable relative to the pointer as the shaft rotates for indicating the angular position of said antenna with respect to a predetermined direction; quadrantal error correcting means controlled by said shaft as it rotates to change the 50 normal position of reference of said pointer and scale to a new point of reference in accordance with predetermined quadrantal error corrections for different angular positions of said shaft and means for adjusting said scale with respect to scalereference reading said predetermined direction. 7 l

LOUIS L. KAESS. 

